Replace fake Forgejo push webhook construction with structured
CloudEvents 1.0 via ChronicleClient. Git commit SHAs are now used
as CloudEvent ids for COMMIT_CREATED and PUSH events, enabling
direct correlation between Chronicle entries and git history.
Event renames:
- REPO_CLONED -> GOV_REPO_CLONED
- COMMIT_CREATED -> GOV_COMMIT_CREATED
- GOVERNED_PUSH -> GOV_PUSH
- PR_CREATED -> GOV_PR_CREATED
Signed-off-by: Tyler King <tking@guildhouse.dev>